/*
 * Title:        CloudSim Toolkit
 * Description:  CloudSim (Cloud Simulation) Toolkit for Modeling and Simulation of Clouds
 * Licence:      GPL - http://www.gnu.org/copyleft/gpl.html
 *
 * Copyright (c) 2009-2012, The University of Melbourne, Australia
 */

package cloudsim.power;

import cloudsim.Host;
import cloudsim.Log;
import cloudsim.Vm;
import cloudsim.util.MathUtil;

import java.util.List;

/**
 * A VM allocation policy that uses Median Absolute Deviation (MAD) to compute
 * a dynamic threshold in order to detect host over utilization.
 * <p>
 * <br/>If you are using any algorithms, policies or workload included in the power package please cite
 * the following paper:<br/>
 * <p>
 * <ul>
 * <li><a href="http://dx.doi.org/10.1002/cpe.1867">Anton Beloglazov, and Rajkumar Buyya, "Optimal Online Deterministic Algorithms and Adaptive
 * Heuristics for Energy and Performance Efficient Dynamic Consolidation of Virtual Machines in
 * Cloud Data Centers", Concurrency and Computation: Practice and Experience (CCPE), Volume 24,
 * Issue 13, Pages: 1397-1420, John Wiley & Sons, Ltd, New York, USA, 2012</a>
 * </ul>
 *
 * @author Anton Beloglazov
 * @since CloudSim Toolkit 3.0
 */
public class PowerVmAllocationPolicyMigrationMedianAbsoluteDeviation extends
        PowerVmAllocationPolicyMigrationAbstract {

    /**
     * The safety parameter in percentage (at scale from 0 to 1).
     * It is a tuning parameter used by the allocation policy to define
     * when a host is overloaded. The overload detection is based
     * on a dynamic defined host utilization threshold. This threshold
     * is computed based on the host's usage history Median absolute deviation
     * (MAD, that is similar to the Standard Deviation).
     * This safety parameter is used to increase or decrease the MAD value
     * when computing the utilization threshold.
     * As the safety parameter increases, the threshold decreases,
     * what may lead to less SLA violations. So, as higher is that parameter,
     * safer the algorithm will be when defining a host as overloaded.
     * For instance, considering a safety parameter of 1.5 (150%),
     * a host's resource usage mean is 0.5 (50%)
     * and a MAD of 0.2 (thus, the usage may vary from 0.3 to 0.7).
     * To compute the usage threshold, the MAD is increased by 50%, being equals to 0.3.
     * Finally, the threshold will be 1 - 0.3 = 0.7.
     * Thus, only when the host utilization threshold exceeds 70%,
     * the host is considered overloaded.
     * Here, more safe or less safe doesn't means a more accurate or less accurate
     * overload detection. Safer means the algorithm will use a lower host
     * utilization threshold that may lead to lower SLA violations but higher
     * resource wastage. Thus this parameter has to be tuned in order to
     * trade-off between SLA violation and resource wastage.
     */
    private double safetyParameter = 0;

    /**
     * The fallback VM allocation policy to be used when
     * the MAD over utilization host detection doesn't have
     * data to be computed.
     */
    private PowerVmAllocationPolicyMigrationAbstract fallbackVmAllocationPolicy;

    /**
     * Instantiates a new PowerVmAllocationPolicyMigrationMedianAbsoluteDeviation.
     *
     * @param hostList             the host list
     * @param vmSelectionPolicy    the vm selection policy
     * @param safetyParameter      the safety parameter
     * @param utilizationThreshold the utilization threshold
     */
    public PowerVmAllocationPolicyMigrationMedianAbsoluteDeviation(
            List<? extends Host> hostList,
            PowerVmSelectionPolicy vmSelectionPolicy,
            double safetyParameter,
            PowerVmAllocationPolicyMigrationAbstract fallbackVmAllocationPolicy,
            double utilizationThreshold) {
        super(hostList, vmSelectionPolicy);
        setSafetyParameter(safetyParameter);
        setFallbackVmAllocationPolicy(fallbackVmAllocationPolicy);
    }

    /**
     * Instantiates a new PowerVmAllocationPolicyMigrationMedianAbsoluteDeviation.
     *
     * @param hostList          the host list
     * @param vmSelectionPolicy the vm selection policy
     * @param safetyParameter   the safety parameter
     */
    public PowerVmAllocationPolicyMigrationMedianAbsoluteDeviation(
            List<? extends Host> hostList,
            PowerVmSelectionPolicy vmSelectionPolicy,
            double safetyParameter,
            PowerVmAllocationPolicyMigrationAbstract fallbackVmAllocationPolicy) {
        super(hostList, vmSelectionPolicy);
        setSafetyParameter(safetyParameter);
        setFallbackVmAllocationPolicy(fallbackVmAllocationPolicy);
    }

    /**
     * Checks if a host is over utilized.
     *
     * @param host the host
     * @return true, if the host is over utilized; false otherwise
     */
    @Override
    protected boolean isHostOverUtilized(PowerHost host) {
        PowerHostUtilizationHistory _host = (PowerHostUtilizationHistory) host;
        double upperThreshold = 0;
        try {
            upperThreshold = 1 - getSafetyParameter() * getHostUtilizationMad(_host);
        } catch (IllegalArgumentException e) {
            return getFallbackVmAllocationPolicy().isHostOverUtilized(host);
        }
        addHistoryEntry(host, upperThreshold);
        double totalRequestedMips = 0;
        for (Vm vm : host.getVmList()) {
            totalRequestedMips += vm.getCurrentRequestedTotalMips();
        }
        double utilization = totalRequestedMips / host.getTotalMips();
        return utilization > upperThreshold;
    }

    /**
     * Gets the host utilization MAD.
     *
     * @param host the host
     * @return the host utilization MAD
     */
    protected double getHostUtilizationMad(PowerHostUtilizationHistory host) throws IllegalArgumentException {
        double[] data = host.getUtilizationHistory();
        if (MathUtil.countNonZeroBeginning(data) >= 12) { // 12 has been suggested as a safe value
            return MathUtil.mad(data);
        }
        throw new IllegalArgumentException();
    }

    /**
     * Sets the safety parameter.
     *
     * @param safetyParameter the new safety parameter
     * @todo It should raise an InvalidArgumentException instead of calling System.exit(0)
     */
    protected void setSafetyParameter(double safetyParameter) {
        if (safetyParameter < 0) {
            Log.printConcatLine("The safety parameter cannot be less than zero. The passed value is: ",
                    safetyParameter);
            System.exit(0);
        }
        this.safetyParameter = safetyParameter;
    }

    /**
     * Gets the safety parameter.
     *
     * @return the safety parameter
     */
    protected double getSafetyParameter() {
        return safetyParameter;
    }

    /**
     * Sets the fallback vm allocation policy.
     *
     * @param fallbackVmAllocationPolicy the new fallback vm allocation policy
     */
    public void setFallbackVmAllocationPolicy(
            PowerVmAllocationPolicyMigrationAbstract fallbackVmAllocationPolicy) {
        this.fallbackVmAllocationPolicy = fallbackVmAllocationPolicy;
    }

    /**
     * Gets the fallback vm allocation policy.
     *
     * @return the fallback vm allocation policy
     */
    public PowerVmAllocationPolicyMigrationAbstract getFallbackVmAllocationPolicy() {
        return fallbackVmAllocationPolicy;
    }

}
